The problem is that Apple's extensive marketing of Apple Intelligence has led to expectations that far surpass what the final product is likely to be.
Most people think generative AI is magic coming out of a hat, so even if Apple delivers at the same level as other companies, people will feel like they've been misled.
There's many reasons not to get an iPhone, but privacy worries, in contrast to Android, is not one of them.
Rather than take an all or nothing attitude on the matter, I certainly think your friend would be better off trying make smart choices with his data whenever possible. Ultimately though, it's something that he has to be motivated to do himself. Perhaps informing him of potential privacy risks would be helpful in that regard.